quick help with regexp?

hi,
i’m trying to split up a filename into it’s parts which should be a matter of seconds for someone who is familiar with perl but to me this regexp-syntax is a complete mystery… could please someone give me a hand with this?

my files are named xx_yyyy.mov where xx is a number and yyyy the framecount. in the end i need the framecount as integer so basically i need something like "strip away .mov and then take the last 4 characters".